One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,7)(3,5,8,6)(10,14)(12,19)(15,21)(16,20)(18,23)(22,24)(30,37)(38,39)(9,10)(11,15)(12,20)(13,16)(14,19)(17,22)(18,24)(21,23)(25,26)(27,30)(28,35)(29,32)(31,36)(33,39)(34,37)(38,40) involution — undirected(2,5)(3,8)(6,7)(9,11,13,17)(10,15,16,22)(12,18,19,23)(14,21,20,24)(25,27)(26,30)(28,33)(29,34)(31,38)(32,37)(35,39)(36,40)(10,16)(11,17)(14,20)(18,23)(25,28,29,36)(26,31,32,35)(27,33,34,40)(30,38,37,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.